1. Field of the Invention
This invention relates to a virtual network management method for managing virtual networks, for example, virtual LANs or the like, which are configured over a backbone network such as an ATM (Asynchronous Transfer Mode) network.
2. Description of the Related Art
In the case of using switching hubs as connecting devices connected to a high-speed network such as an ATM network, it is conventionally known to construct a plurality of separate LANs (virtual LANs) irrespective of physical configuration.
The configuration of a typical virtual LAN will be explained below. In the virtual LAN, a switching hub which is designed according to, for example, the standard ATM-IEEE 802.3 (hereinafter merely referred to as "switching hub") has an ATM interface for high-speed backbone. Utilizing LAN Emulation standardized by the ATM Forum, the switching hub transfers a packet structured according to the standard IEEE 802.3 (hereinafter merely referred to as "packet") to an ATM-side interface.
With LAN Emulation, it is possible to construct a plurality of different emulated LANs (hereinafter referred to as "ELANs"). Namely, according to LAN Emulation, software permits any one of switching hub ports which are designed in conformity with the standard IEEE 802.3 (hereinafter merely referred to as "ports") to be allocated to a desired ELAN. Consequently, a plurality of independent LANs (virtual LANs) can be constructed without reconfiguring physical wiring. A broadcast packet is inhibited from passing through different virtual LANs, and nodes belonging to different virtual LANs are isolated from one another and are unable to communicate directly.
In such virtual LANs, since the individual ports are allocated to different networks by means of software, there arises a difference between the physical wiring and the actual networks, making it difficult to grasp the network configuration. Also, it is unnecessary to reconfigure the hard wiring each time the networks are modified; however, when network modification is made by means of software, virtual LANs must be set manually with a thorough understanding of the hardware connections, requiring considerable time and labor for the settings.
Here let it be assumed that network wiring is installed, for example, in a building and that switching hubs are arranged on the individual floors of the building. The wiring for the switching hubs is extended above ceilings or behind walls and the individual ports are arranged in the form of sockets at predetermined locations on the floors. To each socket is connected a 10 Base-T type hub which in turn is wired to respective nodes in a group or department, followed by the setting of virtual LANs.
With such network wiring installed, there may arise a situation where the nodes of a department at a certain location on the second floor are moved to the first floor and connected to sockets of the switching hub on the first floor. In such a case, the virtual LAN setting for a conventional network system involves checking and setting the port number of the switching hub having sockets to which the nodes were newly connected. It is therefore necessary to grasp with accuracy the wiring relationship between the sockets and physical ports connected thereto.
In practice, however, it is difficult to keep a thorough understanding of the port numbers of the switching hubs in relation to the sockets connected thereto, inclusive of the wiring within the building. Especially in the case of a larger-scale network, the difficulty in the virtual LAN settings through the switching hubs increases for the above reason. If a setting error exists because of erroneous information about the port numbers, there is a possibility that a grave communication fault will occur in the network. Consequently, modification of the virtual LAN settings during operation of the network is always accompanied by great risks that can affect the LAN operation.
In view of the foregoing, there has conventionally been proposed a concept of relational LAN wherein packet protocols or network numbers are detected, and identical network protocols or identical network numbers are automatically allocated to the same virtual LAN, as described on pages 58-81 of Nikkei Communications, No. 186 (Nov. 21, 1994 issue, Japan). The relational LAN facilitates the reconstruction of virtual LANs according to identical protocols or identical network numbers as well as modification of the virtual LANs, thus making it possible to modify the virtual LANs while the network is in operation.
The concept of relational LAN involves the function of isolating networks with the same network number from one another or making different networks coexist on the same virtual LAN, the security function of excluding a network node that was added on purpose to cause a network fault, and other functions. When these functions are executed on the virtual LAN, however, calculations must be performed taking account of upper-layer frames and thus are complicated, entailing difficulty in achieving the functions. It is also necessary that all protocols such as IP (Internet Protocol) and IPX (Internet Packet eXchange) should be recognized and handled, requiring complicated operation.